Liquid electro-photographic (LEP) printing, sometimes also referred to as liquid electrostatic printing, uses liquid toner to form images on paper or other print media. LEP is often used for large scale commercial printing. The basic LEP printing process involves placing a uniform electrostatic charge on a photoconductor, the photoconductive surface on a rotating drum for example, and exposing the photoconductor to light in the pattern of the desired printed image to dissipate the charge on the areas of the photoconductor exposed to the light. The resulting latent electrostatic image on the photoconductor is developed by applying a thin layer of liquid toner to the photoconductor. Liquid toner generally consists of charged toner particles dispersed in a carrier liquid. The charged toner particles adhere to the discharged areas on the photoconductor (discharged area development DAD) or to the charged areas (charged area development CAD), depending on the charge of the toner particles, to form the desired toner image on the photoconductor. The toner image is transferred from the photoconductor to an intermediate transfer member and then from the intermediate transfer member to the paper or other print medium.
In some LEP printers, the photoconductive element includes a replaceable film of photoconductive material wrapped around a rotating drum. This drum is commonly referred to as the PIP (Photo Imaging Plate) and the thin film of conductive material as the PIP foil. The PIP foil is replaced periodically, once or twice a work shift for example depending on the printing volume, to maintain the good print quality. A new PIP foil must be accurately aligned to the PIP drum during installation to help ensure good print quality and to minimize the risk of damaging the PIP foil during installation and printing.
For convenience, similar components may be designated by the same part numbers in the figures.